Rheostat and potentiometer



April 22 A. .1. CARTER v RHEOS'IAv \T AND POTENTIOMETER Flled June 11,1928 g UlmmmlUlWIHNIIIHNHUIIWIWI"lllllllllmulmmu1|11111111.11

l"mmm"IUWllilH"NM1NIIIIHIIIINHIIIIllllllluulw11111111111"- /ZMfJ/Z j@ L/Cargo?" Patented Apr. 22, 1930 UNITED STATES PATENT OFFICE ALVA J.CARTER'OF CHICAGO, ILLINOIS, ASSIGNOR TO' CARTER RADIO COMPANY, OF vCHICAGO, ILLINOIS, A CORPORATION 0F ILLINOIS nHEosTAT AND rorEnTIoi/IETBApplication med June 11,

,resistance is connected in circuit and for increasing the resistance ata gradually higher rate as the resistance included in the circuitincreases.`

It is also an object of this invention to -provide a rheostat orpotentiometer yconstruction such that-the resistance-range and cur-'rent carrying capacity of the rheostat are capable of. meeting a widevariety of voltage and current control requirement. Thus for example inthe case`of\the heating 'current for the filament of vacuum tubes, myrheostat ,may be utilized with tubes having muchdifferent requirementsof current for the same voltage.

In carrying out this invention, I employ a rheostat winding wherein thelength ofeach turn varies from one end to the `other and wherein thespacing of the turns relative to each other may be varied in thedifferent portions .of the rheostat winding.

To further'the adaptability of the devicev for use with differentapparatus requirmg different current capacity for various voltp ages, myinvention also contemplates the use' of wire having a relatively lowresistance for a portion of the wi-nd and a wiring having a relativelyhigh resistance for the remainder thereof.

I attain the aforementioned objects by the.

device illustrated in the accompanying drawings in'which:

Fig. 1 is an elevation ofa rheostat including my device andillust-rating the connections therefor;

Fig. 2 is a section on the line 2-2 of Fig. 1;

Fig. 3 is a detailed v ew ci one' toria of resistance` winding 1928.Serial N0. 284,387.

Fig. is a view similar to Fig. 3 'of a slightly modified form ofwinding; and

Fig. 5 is a detailed view-of a further modiication.

Referring now in detail to the drawings, the rheostat consists of a base10 of. molded phenol condensation product or similar matei rial havingthe upstanding rim 11 and provided with the annular groove 12immediately adjoining the interior of the rim 11 and 1n which theresistance unit 13 is adapted ,to be mounted. The unit 13 consists of acore 14 and winding 15 which will be' hereinafter described in det-ail.This unit 13 extends through most of the circumference of the rim 11 andis secured thereto by means of the terminal screws 16 and 17 at theopposite' ends thereof which screws contact with the ends of the winding15 and may be connected to the'apparatus with which a rheostat is to beused.

The base 10 is connected to a supportin stud 18 by which itmay bemounted upon a suitable support and clamped -thereon by means of thenuts 19 and 20 in ay well known manner. Supporting stud 18 has a head 21within the recess-of the base,10 which Qooperates with the nuts 19 toclamp the base 10 firmlyl thereon. The connecting member 22' is alsoheld in place by the nut 19 and has a portion extending upwardly as at23 along vthfeinner wall of the rim 11 to connect with the wiringterminal 24, the base 10 being slotted to4 permit passage of theupturned ortion 23 of the member 22 therethrough.

A shaft 25. is journaled in the member 18 and has non-rotatably mountedthereon the members 26 and 27 which engage the member 21 to makeelectrical contact therewith. The

member 27 as shownhas the. upturned fiange 28 engaging the projectingportion-29 of member 26 so that they rotate together and vthe member 26is provided with the downturned portion 30 cooperating with the stopprojections 31 and 32 so as to limit the rotation thereof andprevent theconnecting portion 33 of member 27 from moving entirely off .theresistance element 13. AA disc -34 rests o n'top of the member 26 andmay be used for indicating the total resistance of the element graduallyincreases in width from one end to the other so that each turn of wirethereon is of greater length as they approach the large end of thestrip.

Also, in the right hand portion substantially to the point 36 of thewinding 15, thespacing of the turns of the .wire is gradually decreasedfrom the wide spacing at the eX- treme right hand end of the strip to acomparatively small spacing at the point 36, and, from this point to theleft hand end of 'the strip, the spacing is substantially the samebetween the turns.

The advantage of winding the wire in this manner in addition to makingthe strip of varying size -throughout its length lies in the fact thatit permits a greater rotation of the controlling handle 37 for unitchange in resistance when a comparatively small amount of resistance isin the circuit, and, as the amount of resistance in the circuitincreases, the amount of rotation per unit change of resistancedecreases gradually. If the turns were placed the same distance apartthroughout the length of the strip, the initial step of rotation wouldincrease the resistance a much greater proportion of the whole amount ofresistance in the circuit.

v That is not the case with the gradually decreasing spacing between theturns of the wires in the winding as illustrated in Fig. 3. This spacingmakes it possible to more nearly approach a logarithmic increase `in theresistance as the contact member is rotated thereover to increase thetotal amount of rel properly spacing the windings and properly andsucceeding amounts included by the presistance in the circuit, since itis possible by taperlng the strip 14 to make the amount of resistanceadded by each degree, of rotation have the same roportion to the totalresistance included in the circuit as the previous it possible to usethe rheostat interchange-- ably for use with apparatus requiring arelatively low resistance and a high current capacity, and apparatusrequiring a relatively high resist-ance and lower current carryingcapacity. The difference in resistance between the portions of thewindings shown in Figs. 2 and 4 may be provided either by making theportions between the points 38 and 39 of larger wire having the samespecific Also, whenever it is desired, a resistance unit may be made inthe form shown in Fig. 5 wherein the spacing between the turns of wiregradually decreases from thelextreme right hand end of the windingto theextreme left hand end thereof. By utilizing the form shown in Fig. 5,the change in resistance per unit length of the strip may be made tobear a constant ratio to the total resistance between the unit of lengthselected and either end of the strip'which is exceedingly desirable inuse of certain types of apparatus such as the filament current controlin radio sets.

From the above description it is thought that the construction andadvantages of this device will be clear to those skilled in this art.

Having thus described my invention, what I claim as new and desire tosecure by Letters Patent is:

1. A device of the character described comprising an insulating basehaving wound thereon a resistance wire the adjacent turns yof whichgradually decrease in distance apart and increase in length from one endto the other of the strip.

2. A resistance unit comprising a strip of insulating material graduallyincreasing in cross-sectional perimeter from one end to the otherthereof and a resistance wire wound upon said strip each turn of whichis spaced a less distance from the preceding turn from the smaller endof the insulating strip to the larger end.

In witness whereof, I hereunto subscribe my name this'26th day of May A.D., 1928. ALVA J. CARTER.

